This invention relates generally to coated papers which, for example, are suitable for various printing processes, and more specifically the present invention is directed to never-tear plastic papers, that is for example papers containing a plastic supporting substrate rather than natural cellulose, with certain coatings thereover and the use of these papers in ink jet printing processes, dot matrix and impact printers, xerographic imaging and thermal transfer printing processes. Thus, in one embodiment, the present invention relates to never-tear papers comprised of a supporting substrate coated on one or both sides with a coating comprised of a polymer such as hydroxypropyl cellulose, which coating contains a pigment, or pigments, such as titanium dioxide, and a top toner or ink receiving layer, which papers can be selected for dry toner imaging and for wax-based ink donor films. The aforementioned top layer can be modified as indicated herein preferably to optimize the selection of the never-tear papers for use with dot matrix printers and typewriters, which modification can, for example, be preferably accomplished by the addition of fillers, such as colloidal silicas in effective amounts of from about 2 to about 20 weight percent. Additionally, in another embodiment of the present invention there are provided never-tear papers for ink jet printing, which papers contain thereover the coatings illustrated hereinafter with effective amounts of colloidal silica dispersed therein in, for example, an amount of from about 2 to about 60 percent by weight, and preferably in an amount of from about 25 to about 60 percent by weight. Accordingly, some of these coated papers of the present invention may also be incorporated into electrostatographic imaging processes, including color processes which employ liquid toners in some embodiments of the present invention.
In a patentability search report the following United States prior art patents were recited: U.S. Pat. No. 4,701,367 relating to coatings such as styrene/butadiene/styrene triblocks for typewriter ribbon transparencies, see the Abstract of the Disclosure for example; U.S. Pat. No. 4,711,816 relating to transparent sheet materials for plain paper electrostatic imaging apparatuses or copiers, which sheets contain an image receiving layer; U.S. Pat. No. 4,783,376, relating to transparencies with a coating layer of a certain electrical resistance; and U.S. Pat. No. 4,756,961 which discloses an ink accepting coating containing particles of silica, aluminum, silicate, zinc oxide, or titanium oxide.
There are disclosed in U.S. Pat. No. 3,759,744 and U.S. Pat. No. 4,268,595 methods for the preparation of electrographic recording papers for imaging. More specifically, electrographic recording papers can be prepared by applying a dielectric coating on a relatively conductive sheet. Various compounds, such as salts and other compounds capable of retaining or attracting moisture in the sheet may be incorporated into the paper to enhance the conductive properties. In some recording papers the conductive layer is applied on one side of the paper and the dielectric is applied to the other side. Also, the dielectric layer can be applied over the conductive layer. Other conventional recording papers comprise an electrically conductive layer and a dielectric layer thereon on one surface of a base paper and an electrically conductive layer on the outer surface of the base paper. Materials selected as the dielectric layer include highly insulating resins such as silicone resins, epoxy resins, poly vinyl acetate resins, vinyl acetate resins, vinyl chloride resins and styrene-butadiene copolymers. These resins are generally dissolved in an organic solvent and coated on the base paper. It is usually necessary to provide an under-coat layer as a barrier coating on a base paper prior to the coating of a solution of an organic solvent type resin to prevent penetration of the solvent used into the paper. Examples of other electrographic papers are prepared by applying a dielectric film of plastic material such as polyethylene or polystyrene to the paper surface by melt extrusion. Also disclosed in U.S. Pat. Nos. 3,011,918; 3,264,137; 3,348,970 and 3,110,621 are-papers for electrostatic recording employing aqueous coatings both for dielectric layer as well as the conductive layer. The materials of the conductive layer are water soluble or dispersable vinyl benzyl quaternary ammonium compounds and the dielectric layer can be comprised of carboxylated poly(vinyl acetate) in an aqueous ammonical solution.
There is also disclosed in U.S. Pat. No. 3,759,744 an electrostatic recording paper, which paper can be prepared by applying three successive aqueous coats to the machine glazed side of a paper web. The first coating contains titanium dioxide and an electroconductive water dispersible polymer of a vinyl benzyl quaternary ammonium compound. The second coating can be comprised of oxidized starch and calcium carbonate. The third coating may contain calcium carbonate and a carboxylated poly (vinyl acetate) in ammonical solution. The resulting web can then be dried between successive coatings and may be steam treated, see the Abstract of the Disclosure for example.
Further, there is disclosed in U.S. Pat. No. 4,268,595 an electrostatic recording material comprising a support having formed thereon a dielectric layer comprised of a terpolymer containing (a) methacrylic acid, (b) a monomer selected from the group consisting of (1) acrylic acid esters containing at least 4 carbon atoms and (2) methacrylic acid esters containing at least 5 carbon atoms, and (c) a monomer selected from the group consisting of (1) acrylic acid esters containing at least 4 carbon atoms and (2) methacrylic esters containing at least 5 carbon atoms, wherein monomer (b) and monomer (c) are different and at least one of the monomers (b) and (c) is an acrylic acid ester containing at least 11 carbon atoms or a methacrylic acid ester containing at least 8 carbon atoms, and a method for producing an electrostatic recording material, which comprises converting such as a terpolymer to a water soluble or water emulsifiable salt of the terpolymer in which about 20 to 100 mol percent of the carboxyl groups present form a salt with ammonia and/or a volatile amine, dissolving or dispersing the terpolymer salt in water, coating the resulting solution or dispersion onto a support, and drying the coating to volatize the ammonia and/or volatile amine.
Also, there is illustrated in U.S. Pat. No. 4,397,883 an electrographic recording material comprising a conductive paper support coated with an electrically insulating layer comprising a blend of a vinyl ester interpolymer latex and up to 500 parts of an inert finely divided pigment per 100 parts by weight of latex interpolymer. The vinyl ester interpolymer which may comprise about 3 to about 7 weight percent of carboxylic acid groups can be provided by an interpolymerized C.sub.4 -C.sub.10 vinylene monobasic carboxylic acid monomer. Moreover, disclosed in U.S. Pat. No. 4,481,244 is a material that can be selected for writing or printing, which comprises a substrate and coating layer formed thereon of a coating material containing a polymer having both hydrophilic segments and hydrophobic segments.
Additionally, there is disclosed in U.S. Pat. No. 3,790,435 and U.S. Pat. No. 4,318,950 synthetic papers and methods for the preparation thereof. The term synthetic paper as indicated on page 1, line 20, of U.S. Pat. No. 4,318,950 refers to a paper like laminar structure in the form of thin sheets or films of synthetic resinous material employed for various uses such as writing or printing, as distinguished from natural cellulose paper. Synthetic papers comprised of thermoplastic resins or papers coated with polymeric emulsions are known for use in writing and printing. Disclosed in U.S. Pat. No. 3,380,868 are oriented thermoplastic film laminated structures which can be selected for various imaging processes. Polymeric film structures having a matte-finish and a cellular structure achieved with the addition of fillers which roughens the surface upon stretching of the films and renders them receptive to marking by crayons, pencil and ball-point pen are disclosed in U.S. Pat. No. 3,154,461. Laminates comprising layers of oriented films of thermoplastic materials in which at least one of the outermost layers contains a suitable inert additive are disclosed in U.S. Pat. No. 3,515,626. These laminates are useful in films which may be written on by a pencil or a crayon.
Disclosed in U.S. Pat. No. 3,790,435 are synthetic papers with acceptable foldability of a nonlaminated structure of one thermoplastic resin film or a laminated structure of at least two thermoplastic resin films, see the Abstract of the Disclosure for example. Each of the films is stretched or molecularly oriented, and one or more of the films contain a fine inorganic filler to provide paperness of the film. According to this patent some of the films may contain certain amounts of poly(styrene) as a foldability improving agent.
There is disclosed in U.S. Pat. No. 4,663,216 a synthetic paper printable in high gloss, and comprised of (1) a multilayer support, (2) a layer of a transparent film of a thermoplastic resin free from an inorganic fine powder formed on one surface of the support (1), and (3) a primer layer of a specific material, reference the Abstract of the Disclosure for example. The support (1) comprises (1a) a base layer of a biaxially stretched film of a thermoplastic resin, a surface and a back layer (1b), and (1c) composed of a monoaxially stretched film of a thermoplastic resin containing from 8 to 65 percent by weight of an inorganic fine powder.
Further, there is disclosed in U.S. Pat. No. 4,705,719 a synthetic paper of multilayer resin films comprising a base layer (1a) of a biaxially stretched thermoplastic resin film, and a laminate provided on at least one of opposite surfaces of said base layer, the laminate including a paper-line layer (1b) and a surface layer (1c), the paper-like layer containing a uniaxially stretched film of a thermoplastic resin containing 8 to 65 percent by weight of inorganic fine powder, said surface layer being constituted by a uniaxially stretched film made of a thermoplastic resin. Also known is an electrostatic recording material comprised of a multi-layered sheet support having an electroconductive layer and dielectric layers formed successively thereon, reference for example U.S. Pat. No. 4,795,676.
Never-tear plastic papers (3R109 durable paper available from Xerox Corporation) comprised of a polyester base containing a coating blend of certain binders with titanium dioxide are also known. These aforementioned papers are useful in a single sided xerographic imaging process, however, they possess disadvantages when selected for duplex imaging systems in that, for example, there is an electrostatic buildup of charges during the first printing cycle on one side thereby preventing the paper from a consistent automatic feeding through the xerographic imaging device a second time. Another type of never-tear plastic paper is comprised of an opaque polyester base containing a binder, an antistatic agent and titanium dioxide. These papers possess acceptable charging and discharging characteristics for duplex printing but have disadvantage that the toner in the imaged areas does not fix well to the paper. The disadvantages of these two types of never-tear papers are overcome with the never-tear papers of the present invention wherein the receiving layer is free of pigment such as titanium dioxide as well as an antistatic agent thereby resulting in excellent toner fix primarily because of the presence of, for example, hydroxypropyl cellulose in the pigmented layer underneath the toner receiving layer. The pigmented layer also acts as an antistatic layer, in some embodiments and ensures proper charging and discharging behavior, and thus there is no electrostatic buildup on these never-tear papers resulting in their being ideal for duplex printing.
Also a number of transparencies with, for example, coatings are known, reference for example U.S. Pat. Nos. (1) 3,535,112, which illustrates transparencies with polyamide overcoatings; (2) 3,539,340 wherein transparencies with vinyl chloride overcoatings are described; (3) 4,072,362 which discloses transparencies with overcoating of styrene acrylate or methacrylate ester polymers; (4) 4,085,245 wherein there is disclosed transparencies with blends of acrylic polymers and vinyl acetate polymers; (5) 4,259,422 which discloses, for example, transparencies with hydrophilic colloids; (6) 4,489,122 wherein there is disclosed transparencies containing elastomeric polymers overcoated with poly(vinylacetate), or terpolymers of methylmethacrylate, ethyl acrylate, and isobutylacrylate; and (7) 4,526,847 which discloses transparencies containing coatings of nitrocellulose and a plasticizer.
There are described in the U.S. Pat. No. 4,956,225 transparencies suitable for electrographic and xerographic imaging comprised of a polymeric substrate with a toner receptive coating on one surface thereof, which coating is comprised of blends of poly(ethylene oxide) and carboxymethyl cellulose; poly(ethylene oxide), carboxymethyl cellulose and hydroxypropyl cellulose; poly(ethylene oxide) and vinylidene fluoride/hexafluoropropylene copolymer, poly(chloroprene) and poly(.alpha.-methylstyrene); poly(caprolactone) and poly(.alpha.-methylstyrene); poly(vinylisobutylether) and poly(.alpha.-methylstyrene); blends of poly(caprolactone) and poly(p-isopropyl .alpha.-methylstyrene); blends of poly(1,4-butylene adipate) and poly(.alpha.-methylstyrene); chlorinated poly(propylene) and poly(.alpha.-methylstyrene); chlorinated poly(ethylene) and poly(.alpha.-methylstyrene); and chlorinated rubber and poly(.alpha.-methylstyrene). Further, in another aspect of the U.S. Pat. No. 4,956,225 there are provided transparencies suitable for electrographic and xerographic imaging processes comprised of a supporting polymeric substrate with a toner receptive coating on one surface thereof comprised of: (a) a first layer coating of a crystalline polymer selected from the group consisting of poly(chloroprene), chlorinated rubbers, blends of poly(ethylene oxide), and vinylidene fluoride/hexafluoropropylene copolymers, chlorinated poly(propylene), chlorinated poly(ethylene), poly(vinylmethyl ketone), poly(caprolactone), poly(1,4-butylene adipate), poly(vinylmethyl ether), and poly(vinyl isobutylether); and (b) a second overcoating layer comprised of a cellulose ether selected from the group consisting of hydroxypropyl methyl cellulose, hydroxypropyl cellulose, and ethyl cellulose.
Additionally there is described in the copending application, U.S. Pat. No. 4,997,697 entitled "Transparencies" with the listed inventor Shadi Malhotra, a transparency comprised of a supporting substrate, an antistatic polymer layer coated on one or both sides of the substrate comprised of hydrophilic cellulosic derivatives, and toner receiving polymer layer thereover on both sides of the antistatic layer comprised of hydrophobic cellulose ethers and cellulose esters in combination with low melt adhesives. Other transparency coatings include blends of poly(ethylene oxide) with carboxymethyl cellulose as illustrated in U.S. Pat. No. 4,592,954, the disclosure of which is totally incorporated herein by reference, blends of carboxymethyl cellulose, poly(ethylene oxide) and hydroxypropyl cellulose, reference U.S. Pat. No. 4,865,914 blends of hydrophilic cellulosic and plasticizers, reference U.S. Pat. No. 5,006,407, the disclosure of which is totally incorporated herein by reference. Further, disclosed in the patent is a transparency comprised of a supporting substrate on an oil absorbing polymer layer on both sides of the substrate and an ink receiving polymer layer thereon. The ink receiving layer may contain fillers.
Although the papers illustrated in the prior art are suitable for their intended purposes, there remains a need for papers with new coatings thereover that are useful in ink jet printing processes, electrophotographic imaging and printing processes, including color processes, and that will enable the formulation of images with high optical densities. Additionally, there is a need for never-tear papers that can be selected for duplex copying processes. Another need of the present invention resides in providing papers with coatings that do not block (stick) at, for example, 50 percent relative humidity and at a temperature of 50.degree. C. Further, there is a need for never-tear papers that avoid or minimize jamming at the fuser roll, thus shorting the life thereof. Also, there is a need for static-free never-tear papers, or wherein the static charge thereon is minimized or substantially avoided. Another need resides in the provision of never-tear papers for ink jet, dot matrix, typewriters and crayon printing processes, and wherein images of high optical density, such as greater than one, are obtained in embodiments of the present invention.